During your trip to Thailand and among the things to visit and not to miss is the Mon Bridge.
The Uttamanusorn Bridge (or Saphan Mon) in Sangkhlaburi province is the longest wooden bridge in Thailand with 850 meters long. It was built in 1986 and finished in 1987 to connect the Mon and Thai villages on both sides of the Tsongalia River, created by the Vajiralongkorn Dam (formerly Khao Laem Dam) which opened in 1984.
The Khao Laem lake water levels change throughout the season and make the structure of the bridge visible or hidden which adds something special to this place with the scenic river views.
Within a 20 min boat ride from the bridge, you can also visit Wat Saam Prasob which depends on whether the season is submerged or not.
The bridge is open every day 24 h, so you are free to visit at any time and I strongly recommend going there in the early morning to avoid too many people (locals and Thais tourists mostly) and get shots of the empty bridge, then around 7 am witness locals walk across the bridge to make merit by offering food to the monks as a daily routine.
You will also meet some ladies selling flowers if you wish to participate, and girls in the traditional dress ready to pose for your photos ( for a few bucks) but even staged it can make a beautiful photo.
There are souvenirs shops around and a few local restaurants and coffee shops, but I recommend you take your breakfast at your hotel if time allows as you might not find your usual breakfast there.